The general rule is... if D > 0, then you have two different real roots (see note below) If D = 0, then you have exactly one real root If D < 0, then you have no real roots (the two roots are imaginary/complex) where D is the discriminant found by the formula D = b^2 - 4ac
Note: If D is also a perfect square, then the two real roots are also rational. This assuming that a,b,c are rational.
